Wastewater Treatment Improvements

CHALLENGE

The city’s wastewater treatment plant was constructed in the 1950s and has undergone several modifications throughout its 50+ years. With aging facilities that were organically overloaded, plant operators were having difficulty consistently meeting NPDES permit limits. FOX Engineering was retained in December of 2005 to complete a comprehensive facility plan to address the wastewater treatment needs of the community.

UV Disinfection

SOLUTION

With involvement from city council and city staff, the project team identified three main alternatives for improving and expanding the existing activated sludge treatment plant capacity. As part of the facility planning effort, FOX prepared a detailed evaluation of each alternative, quantifying the costs and benefits of each. After careful consideration and input from FOX, the city elected to continue utilizing a conventional activated sludge process. After completion of the Facility Plan in December 2006, FOX was retained to design the recommended improvements. The major expansion and renovation of the plant includes new preliminary treatment facilities, construction of new aeration basins and a new final clarifier, ultraviolet (UV) disinfection, and refurbishing of the aerobic digesters and solids handling facilities. Construction began spring 2008 and was complete spring 2010.

Biosolids complex

OUTCOME

Design was finalized in early 2008 and bid on April 8, 2008; the city received five bids. Construction occurred throughout 2008 and 2009, and the project was completed on May 31, 2010. With FOX Engineering’s help, the City received a Community Development Block Grant (CDBG) and Clean Water State Revolving Fund (CWSRF) loan to fund the project.

With the new facilities in place, the plant has reliably met discharge limits and provided the City with significant capacity for future growth. The plant is also much easier to operate and maintain.

Aeration basins

Sludge storage

ONGOING

Since construction was completed, FOX has continued teaming with Manchester in dealing with equipment warranty issues and in providing advice and guidance to staff to optimize plant performance. In 2015, Manchester was facing difficulties in replacing its Grade IV operator. To address this problem, FOX worked with the city and the IDNR to “de-rate” the plant capacity by 6%, thereby changing the operator classification requirement to Grade III. The plant had ample capacity, so this minor change will not hamper the City’s ability to grow in the near or long term.

During the same time period, Manchester received a renewed NPDES permit. FOX reviewed the permit and found several errors that, once corrected, reduced plant sampling and testing requirements. FOX also successfully petitioned the IDNR to reduce sampling/testing requirements for the activated sludge aeration basins by requesting and receiving a formal variance.

Blowers

RECOGNITION

The project received the 2011 Iowa ACEC Engineering Achievement Award for Excellence in the Water/Wastewater Category.

FOX worked with the city and the IDNR to “derate” the plant capacity by 6%, thereby changing the operator classification requirement to Grade III. The plant had ample capacity, so this minor change will not hamper the City’s ability to grow in the near or long term.

During the same time period, Manchester received a renewed NPDES permit. FOX reviewed the permit and found several errors that, once corrected, reduced plant sampling and testing requirements. FOX also successfully petitioned the IDNR to reduce sampling/testing requirements for the activated sludge aeration basins by requesting and receiving a formal variance.